Unused variable in Image effect color validate function

Here is the validation image_effect_color function.
We can see that $hex_value is clearly unused, and so preg_replace function is not used for anything.

/**
 * Element validate handler to ensure a hexadecimal color value.
 */
function image_effect_color_validate($element, &$form_state) {
  if ($element['#value'] != '') {
    $hex_value = preg_replace('/^#/', '', $element['#value']);
    if (!preg_match('/^#[0-9A-F]{3}([0-9A-F]{3})?$/', $element['#value'])) {
      form_error($element, t('!name must be a hexadecimal color value.', array('!name' => $element['#title'])));
    }
  }
}